1. Field of the Invention
This invention is concerned with a camshaft comprising a hollow tubular shaft and an inner member received within the tubular shaft so that a lubricant guiding space is defined between the tubular shaft and the inner member and is connectable via radial bores in the tubular shaft to bearing regions on the outside of the tubular shaft and to at least one lubricant supply. Such a camshaft is known from West German patent specification No. 35 01 433 in which the inner member is in the form of a tube and, in addition to said bores, further radial bores are provided leading to the cam tracks. Camshafts of this type take account of the problem that in hollow camshafts there is not sufficient material for introducing oil guiding bores and that the entire cross-section of the hollow shaft should not be used for lubricant guiding purposes because this would result in unacceptable delays in the supply of oil especially when starting the engine when the oil supply cross-sections are empty.
2. Description of Prior Art
The camshaft described in the above-mentioned West German patent specification is used in the form of a plastic cylindrical tube or bar member which is produced by an injection molding process and engages in plugs or covers at the ends of the hollow camshaft. If the camshaft is long, it is necessary to provide additional spacers along the length of the camshaft. The production methods involved in achieving this are complicated since the spacers can only be produced by means of special molds inserted into the hollow shaft tube, these moulds being expensive and only being justified for large production runs.
It is an object of the present invention to develop a camshaft of the type aforementioned in which spacers and plugs at the ends of the shaft may be eliminated, even in the case of long camshafts, and to provide the possibility of reducing the cross-sections of the lubricant supplies.